An internal combustion engine has been widely used in vehicles, ship, small power generators, and the like, and attempts to improve efficiency of the internal combustion engine have been continuously conducted. In the internal combustion engine, a large quantity of heat is generally exhausted as waste heat, and a waste heat recovery system for increasing efficiency of the internal combustion engine by recovering the waste heat as energy has been developed.
The waste heat recovery system is configured to recover waste heat exhausted from an engine as energy, convert the recovered energy into electric energy or mechanical energy, and utilize the electric energy or the mechanical energy in the engine, other electrical accessories, or the like, of the vehicle.
The waste heat recovery system is configured to include a Rankine cycle to effectively recover the waste heat of the engine. The Rankine cycle includes a circulation path through which an operating medium is circulated, and the circulation path of the Rankine cycle is provided with a boiler (evaporator) for heating and evaporating the operating medium by the waste heat (heat of an exhaust gas and/or heat of an exhaust gas recirculation (EGR) gas) of the engine, an expander for expanding the operating medium supplied from the boiler to generate rotation power, a condenser for condensing the operating medium exhausted from the expander, and a pump for circulating the operating medium on the circulation path.
A scheme of transferring the recovered energy of the waste heat recovery system described above as auxiliary power to the engine or utilizing the recovered energy to store electric energy of a power generator has been used. However, in the case of such a scheme, a utilization strategy of the recovered energy is not efficient.